380 KAM.^ICin KISHINOI'YE: 



median septum. In Thunnus orientalis the two ureters meet in a figure like 

 U, and in the other forms of the Japanese tunnies they meet Hke the figure 

 Y. In Katsuwonus the two ureters run quite near by in the posterior slender 

 part of the kidneys, and finally unite to a median canal of some length. In 

 Eufhynims and Auxis the two ureters are nearly separate. 



liie urinary bladder is variable in size, form and position. Generally it 

 is small and lies behind the peritoneum, but in AcantJioci/Uum, Neotlmnnus, and 

 Auods the bladder is large or much elongated and is found in the abdominal 

 cavity, suspended in the mesentery or between the two genital glands and above 

 the rectum. 



REPRODUCTIVE SYSTEÄI. 



In the scombroid fishes the generative organs are paired, large, and elon- 

 gated sacs on the roof of the abdominal cavity, suspended in a fold of the 

 peritoneum, and extend along almost the whole length of the cavity. The organs 

 on both sides are symmetrical, nearly equal to each other in form and size. In 

 Awxis the generative organs, both male and female, extend backwards along 

 the side of the anal fin. This backward extension is not so marked as in tbe 

 case of the female flatfish, but its cause is the sitme— the naiTowness of the 

 abdominal cavity. In scombroid fishes the genital glands generally seem tj 

 lij^jen in the third year of gi'owth, that is when the fish is two yeai-s old. 



The testes have trenchant edges, hence more or less lanceolate in cixjss- 

 section, and when ripe, milky white to light yellowish in colour. The ovaries 

 are fusiform, more or less roimdish in cross-section, and yellowish in colour, and 

 greater in volume than the testLs. In tunnies the gonads grow very large, 

 attaining several kg. in weight. As the eggs in them are minute as in other 

 fishes, their numlier is no doubt enormously large. 



Scombroid fishes generally spawn in the warm season, and in the open 

 sea. So far as I know, Sco/iiber japonicus, Q/himn niphoninm, and C. kareaimm 

 are the only spscies which spawn in oiu' bays and inland seas. Spawned e^:s 

 and larvae of the plecosteau fishes are still imknown. 



The generative organs of both sides coalesce near the hind end, and the 

 hmiam in them unite to a short and wide duct, which opens as a transverse 

 slit on a papilla, Ijohiud the anus. 



